1. Field of the Invention
The invention relates to digital information distribution systems and, more particularly, the invention relates to an asynchronous serial interface (ASI) ring network for routing digital information to multiple users.
2. Description of the Background Art
Digital video can be distributed through networks that utilize asynchronous transfer mode (ATM) and packet over SONET. However, both of these types of digital video distribution systems are not cost effective and require significant overhead bandwidth for each respective packet format plus configuration and control overhead to facilitate network routing. A more efficient network solution for point-to-point transmission and delivery of Moving Pictures Experts Group (MPEG) packets is known as DVB-ASI (Digital Video Broadcast/Asynchronous Serial Interface). DVB-ASI is described in European Standard EN 50083 entitled xe2x80x9cCable Distribution System for Television, Sound, and Interactive Multimedia Signalsxe2x80x9d, March 1997. This specification defines a protocol for distributing digital video in the form of MPEG packets at a rate of 270 Mbps. The actual data carriage under this protocol is 216 Mbps. Although the DVB-ASI protocol is well suited for simplex, point-to-point communications, a system based on this protocol is not capable of supporting high speed data transmissions that are necessary for multi-user digital video distribution systems. Furthermore, because of the limited data carrying capability, the DVB-ASI protocol does not efficiently utilize the bandwidth that is available for optical fiber based systems, i.e., a bandwidth that exceed 1 Gbps.
Therefore, there is a need in the art for a multi-user, digital video distribution system that provides high speed transmissions, e.g., more than a gigabit per second, in conjunction with a low overhead transmission protocol.
The disadvantages associated with the-prior art are overcome by a packet structure that facilitates a multiple source, multiple sink, digital information distribution system having an asynchronous serial interface (ASI) ring network topology. The system is capable of delivering multimedia data (video and audio information) as well as internet protocol (IP) data using packets that comply with the Moving Picture Expert Group (MPEG) packet standard. The MPEG packets form the payload within a unique packet structure. The packet structure enables efficient routing of the packets through an ASI ring network. Specifically, the packet structure comprises a packet header, a routing information field, a private data field, digital video payload, and an error correction code field. Such a packet structure enables the network to deliver digital information through the ASI ring network to a user that is identified in the routing information field.
The packet structure is routed through a ring network comprising a plurality of nodes that are interconnected via counter-rotating communications paths. Within each network node is a ring terminal that facilitates routing of packets through the network. The ring terminal extracts packets from the communications paths that are addressed to a particular node and injects packets into the paths that are to be communicated to other nodes. The ring terminals also handle network faults by re-routing packets to avoid communications paths and/or network nodes that fail.